Dependence of the Al<i>x</i>Ga1−<i>x</i>As band edge on alloy composition based on the absolute measurement of <i>x</i>

Abstract

The absolute determination of the Al concentration, x, in epitaxial layers of AlxGa1−xAs was carried out using a nuclear reaction technique. This technique utilizes the narrow resonances found in the 27Al( p,γ)Si28 reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition. The AlxGa1−xAs band edge was measured on these samples through low-temperature photoluminescence (2 K) measurements. An improved value of the direct edge (Γ) on composition was determined to be EΓg =1.512 +1.455x(eV) within a ±0.3% limit. The direct-to-indirect transition was found to occur at an Al concentration of x≂0.37±0.015, lower than previously reported for He temperatures.